Evaporation heat transfer and pressure drop of R-410A in three 7.0 mm O.D. microfin tubes having different inside geometries

Abstract

R-410A evaporation heat transfer and pressure drop data are provided for three 7.0 mm O.D. microfin tubes. The microfin tubes had different helix angle, fin height and fin apex angle. Tests were conducted for a range of quality (0.2 ~ 0.8), mass flux (216 ~ 390 kg/m 2 s), heat flux (9 ~ 17 kW/m 2 ) and saturation temperature (8 ~ 12 o C). It was found that three microfin tubes yielded approximately the same heat transfer coefficients. Microfin tube with larger inter-fin spacing or smaller helix angle yielded lager pressure drop. Both heat transfer coefficient and pressure drop increased as mass flux or quality increased. However, they decreased as saturation temperature increased. The range of heat transfer enhancement factor (1.37 ~ 1.97) was comparable with that of pressure drop penalty factor (1.22 ~ 1.77). Data are compared with available heat transfer and pressure drop correlations.